Neutron diffraction investigation of the magneto-elastic effect in LaMnO3

We have investigated the magneto-elastic effect at the antiferromagnetic phase transition in LaMnO(3) by neutron powder diffraction. The intensity of the (001) magnetic reflection decreases continuously to become zero at T(N)approximate to 141 K indicating a second-order antiferromagnetic phase transition. The lattice parameters a and b (space group Pbnm) of LaMnO(3) show well-defined anomalies close to T(N)approximate to 140 K, whereas the third lattice parameter c and the unit-cell volume show only weak anomalies. The present investigation shows strong magneto-elastic effect in LaMnO(3) close to T(N).